Field of the Invention
The present invention relates to a plasma processing apparatus and a method therefor.
Description of Related Art
The plasma processing apparatuses disclosed in Japanese Patent No. 4858395 and United States Patent Application Publication No. 2012/0238073 have process targets of a substrate (wafer, for example) held in a carrier including an annular frame and a holding sheet. The substrate is held on a holding sheet. In addition, these plasma processing apparatuses include a cover that covers a frame and an area between the substrate outer-periphery of the holding sheet and the frame so that the frame and the area are not to be exposed to the plasma.
The cover is heated by being exposed to plasma, and tends to have a high temperature. Radiant heat from the heated cover gives thermal damage to the resist of the substrate outer peripheral part, holding sheet, and frame. As measures against the thermal damage by the radiant heat from such a cover, the substrate and the carrier are electrostatically attracted to and brought into close contact with the stage (cooled by coolant circulation), and can be cooled by the heat transfer to the stage. In order to improve heat transfer between the stage and the substrate placed on the stage, it is known to supply a heat transfer gas being a noble gas such as helium between the stage and the substrate (backside gas cooling).
In the conventional plasma processing apparatus, when the target of the plasma process is a substrate held by the carrier, there has not been any specific study on in what manner the back side gas cooling should be performed so that the plasma process performance and the cooling performance can be compatible.